This invention relates to a rotary vane evacuating pump of the type having at least one pumping stage which is cooled by a cooling fluid such as water surrounding the cylindrical sleeve of the pumping stage.
Conventional rotary vane evacuating pumps of this type are provided with a water jacket defined between the outside of the cylindrical sleeve wherein the rotor of the pump is received and an outer housing spaced from the sleeve and surrounding the same. The sleeve and the outer housing are generally integrally formed by casting techniques.
Rotary vane evacuating pumps are commonly used in the fields of chemical and pharmaceutical industries for purposes such as distillation, drying and fractionating, as well as for varying purposes in the plastics, ceramic and packaging industries. These pumps are often exposed to aggressive and corrosive fluids causing a deterioration of the pump performance after prolongated operation. In chemical processes, for example, the pump performance may become unsatisfactory after a continuous operation for about one year or even less, requiring the pump to be serviced or replaced. While a replacement of the pump is the easiest manner to restore the operativeness of the implement to which the pump belongs, it is also the most expensive one. In fact, the conventional rotary vane evacuating pumps are rather expensive, due to the complicated structure and shape of the pump housing which is required to incorporate a cooling water jacket. The production of these pump housings requires complex and expensive casting techniques to be applied. On the other hand, a replacement of the worn parts of the pump requires considerable time for dismantling the pump housing, disassembling the worn parts and reassembling the whole pumping unit. Prolongated shutoff times can hardly be tolerated in many chemical processes.
It is, therefore, a primary object of the invention to provide an improved rotary vane evacuating pump having at least one pumping stage provided as a readily exchangeable unit.
It is a further object of the invention to provide an improved rotary vane evacuating pump having two series connected pumping stages each of which is provided as a readily exchangeable unit.
A still further object of the invention is to provide an improved pumping stage for a rotary vane evacuating pump, the pumping stage being reduced to the basic active parts of a rotary vane pump so that complete pumping stages can be economically provided as spare parts for replacement of used pumping stages.
Other objects and advantages of the present invention will become apparent as the description proceeds.